4.2. Thermal mode of the engine
During the correct work of all knots and elements of the cooling system the normal thermal mode of the engine (temperature of cooling liquid of 80-100 °C, an arrow of the index of temperature of cooling liquid is in a white zone of a scale) after warming up is automatically supported by the thermostat.
Periodically, and also in case of violation of the normal thermal mode of the engine (an overheat in normal service conditions or long warming up of the engine after start-up) it is necessary to check operation of the thermostat and electric fan of the cooling system. To check operation of the thermostat 3 (see rice. The bottom view on a cooling system radiator) it is possible to the touch directly on the car. After launch of the cold engine at the serviceable thermostat the taking-away (lower) hose of the 5th radiator begins to heat up when temperature of cooling liquid rises to 80–85 °C. Earlier or later heating of the taking-away hose of a radiator indicates the malfunction of the thermostat connected with lag of the valve in open situation or its jamming in a closed position. If it is impossible to eliminate malfunction, then it is necessary to replace the thermostat.
If the electric fan 1 does not turn on at achievement by an arrow of the index of temperature of cooling liquid of the last mark before a red zone of a scale (107 °C), then it testifies to malfunction of its sensor 2 inclusions, the relay or the electric fan.
At all checks previously it is necessary to be convinced of serviceability of the index of temperature of cooling liquid.